DESCRIPTION

The
nextafter()
functions return the next representable floating-point value following
x
in the direction of
y.
If
y
is less than
x,
these functions will return the largest representable number less than
x.

If x equals y, the functions return y.

The
nexttoward()
functions do the same as the
nextafter()
functions, except that they have a
long double
second argument.

RETURN VALUE

On success,
these functions return the next representable floating-point value after
x
in the direction of
y.

If
x
equals
y,
then
y
(cast to the same type as
x)
is returned.

If
x
or
y
is a NaN,
a NaN is returned.

If
x
is finite,
and the result would overflow,
a range error occurs,
and the functions return
HUGE_VAL,
HUGE_VALF,
or
HUGE_VALL,
respectively, with the correct mathematical sign.

If
x
is not equal to
y,
and the correct function result would be subnormal, zero, or underflow,
a range error occurs,
and either the correct value (if it can be represented),
or 0.0, is returned.

ERRORS

See
math_error(7)
for information on how to determine whether an error has occurred
when calling these functions.

The following errors can occur:

Range error: result overflow

An overflow floating-point exception
(FE_OVERFLOW)
is raised.

Range error: result is subnormal or underflows

An underflow floating-point exception
(FE_UNDERFLOW)
is raised.

These functions do not set
errno.

CONFORMING TO

C99, POSIX.1-2001.
This function is defined in IEC 559 (and the appendix with
recommended functions in IEEE 754/IEEE 854).

BUGS

In glibc version 2.5 and earlier, these functions do not raise an underflow
floating-point
(FE_UNDERFLOW)
exception when an underflow occurs.